Human leukocyte antigen (HLA)-haploidentical stem cell transplantation (haplo-SCT) has been shown to be associated with a higher risk of early transplant-related mortality. This is because of complications in severe graft-versus-host disease arising due to allogeneic immune reactions and graft rejection. Therefore, traditionally, SCT from HLA-matched donors has been recommended. Contrastingly, allogeneic immune reactions induce a strong graft-versus-leukemia effect; thus, haplo-SCT is the treatment of choice for patients with relapsed/refractory leukemia. With recent advances in treatment methods, the survival rate in pediatric acute leukemia has improved. However, the prognosis of patients diagnosed with post-transplant relapsed/refractory leukemia or other relapsed diseases with poor prognostic factors continues to be dismal. We retrospectively analyzed 39 patients with relapsed/refractory acute leukemia who underwent T-cell-replete haplo-SCT between 2009 and 2016. The 3-year overall and disease-free survival rates were found to be 45.1±8.5% and 33.8±7.9%, respectively. Although these results are derived from case studies performed in a single institution, they will be important in evaluating the efficacy of prospective multi-center trials of T-cell-replete haplo-SCT.